Good morning Robert,
- to replace a file an an file area within Moodle, proceed as if you were adding a new file, and then when Moodle realizes that the new file has the same name as one of the files already in the file area, it will ask you whether you wish to overwrite the old file with the new one, or rename the new file to something else.
- perhaps you don't need a regrade option, because I think the regrading is done automatically when you change a setting that will affect the grades. I'm not sure about that though, so we better test it to make sure
regards
Gordon